This invention relates to a new and improved pruning boom for pruning or trimming trees, bushes, shrubs and the like. The pruning boom of the present invention is particularly suitable for use as a component of pruning machines of the type commonly used for citrus grove caretaking operations.
It is the general practice in the citrus industry to plant trees in relatively close-spaced parallel rows for maximum utilization of the acreage available to the grove owner. Citrus trees which are planted in relatively close-spaced parallel rows have a tendency to grow rapidly, and thereby, to fill the space between adjacent trees with dense vegetation. Of course, this dense vegetation shuts out sunlight and prevents passage of vehicles and other machines between adjacent rows of trees.
It is well known that the dense vegetation which grows between adjacent rows of citrus trees must be pruned or hedged periodically to maintain the health of the trees in the grove and to achieve normal fruit production for the grove. Furthermore, such periodic pruning or hedging is required to maintain open passageways between adjacent rows of trees in the grove. Such passageways are essential for normal citrus grove caretaking operations inasmuch as vehicles and other machines are used for cultivating, fertilizing, spraying and otherwise caring for the trees in the grove.
It is also well known that citrus trees often grow rapidly on top and take on what is sometimes referred to as wild growth. Periodic pruning or topping of such wild growth is necessary to maintain the health of the trees in the grove and to achieve normal fruit production for the grove. And, of course, such pruning or topping lowers the overall height of the trees in the grove for more convenient fruit harvesting operations.
Two general types of pruning machines, i.e. hedging machines and topping machines, are widely used in the citrus industry for mechanized tree pruning operations. Hedging machines are used for pruning the dense vegetation which grows between adjacent rows of trees. Topping machines are used for cutting the wild growth on the tops of trees. Pruning machines, such as the machine in U.S. Pat. No. 4,067,178, which are capable of both hedging and topping are known but are not widely used in the citrus industry.
The various pruning machines which are widely used in the citrus industry utilize pruning arms or booms having a plurality of rapidly rotating circular saw blades for cutting branches, limbs and other vegetation from the trees. In general, hedging machines utilize pruning booms which are positioned essentially vertically during operation and topping machines utilize pruning booms which are positioned essentially horizontally during operation. Often, topping machines are operated with their pruning booms positioned at slight angles from the horizontal to cut branches, limbs and other vegetation from the tops of the trees in a manner which causes the tree tops to have a somewhat pyramidal shape.
It has long been known that the cutting paths of the saw blades of known pruning machines must be overlapped in some manner during pruning operations if the trees are to be pruned uniformly. Various means for overlapping the cutting paths of the saw blades of pruning machines have been known for many years. For example, each of the pruning booms on the hedging and topping machine in U.S. Pat. No. 4,067,178 has a slight "dog leg" configuration which results in overlapping cutting paths for the saw blades during pruning operations. The hedging machine in U.S. Pat. No. 3,138,911 utilizes straight pruning booms having alternating peripherally overlapped saw blades. This saw blade configuration is widely used on pruning machines used in the citrus industry. Other means for overlapping the cutting paths of saw blades include the use of reciprocating pruning booms (U.S. Pat. No. 3,157,016), oscillating pruning booms (U.S. Pat. No. 3,214,895), and rotating saw carriers (U.S. Pat. Nos. 2,926,480 and Re. 26,793).
During pruning operations using pruning machines having known pruning booms, a significant number of the newly cut branches and limbs wedge between the rotating saw blades and the saw carrying member of the boom immediately after they are cut from the tree. Often, these branches and limbs are retained in their wedged positions for extended periods of time and impart substantial frictional forces to the rotating saw blades and their drive shafts. And, of course, increased rotational horsepower is required to overcome these frictional forces and maintain a constant rotational speed for the saw blades.
It is not uncommon for branches and limbs which are wedged between the rotating saw blades and the saw carrying member of known pruning booms to engage uncut branches and limbs on a tree, and, thereby, move such branches and limbs from the cutting paths of the advancing saw blades. Usually, such branches and limbs return to their original positions when the advancing saw blades have passed. When this occurs with significant frequency, a newly pruned citrus grove can be very unsightly. Furthermore, the protruding branches and limbs which remain on the pruned trees are often a nuisance, and occasionally a hazard, during subsequent caretaking and harvesting operations in the grove.
Many designers of pruning machines provide a rotating steel bar or beater on each of the drive shafts for the rotating saw blades of known pruning booms. When such beaters are used, they are mounted between the saw blades and the saw carrying member of the boom. The pruning machines in U.S. Pat. Nos. 3,157,016 and 3,214,895 utilize typical beaters, often called "limb knockers". While such beaters dislodge many of the newly cut branches and limbs which wedge between the rotating saw blades and the saw carrying member of the boom, they do not eliminate the problem. In fact, many designers and operators of pruning machines are of the opinion that the benefits obtainable from beaters do not compensate for their detriments. Longer drive shafts are required for the rotating saw blades when beaters are utilized. This increases bearing stresses and often causes severe wear on the bearing surfaces. And, of course, the beater and the longer drive shafts which are required for their use add significant weight to the pruning boom.
It is usually necessary for the operator of a pruning machine having known pruning booms to shut down the machine periodically during pruning operations for removal of branches and limbs which are wedged between the rotating saw blades and the saw carrying member of the boom. When the frequency of these shut downs is high, the resulting loss of pruning time can be very costly. And, of course, removal of wedged branches and limbs by the pruning machine operator exposes the operator to a substantial risk of personal injury inasmuch as such branches and limbs must be pulled from their positions between the rotating saw blades and the saw carrying member of the boom.